UK light-heavyweight Buatsi made a winning yet unimpressive start to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a split decision in a tight ten-round fight at the Manchester venue.
But Parker had his moments, delivering effective individual punches in a fight where the approaches didn't complement each other, with frequent clinching disrupting the action.
The officials scored it 96-94 for to the winner, with the final judge a even score.
"It wasn't my greatest showing but what do champions do? They win," the victor commented in the arena as he was met by disapproval from the spectators.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in February - to earn a 20th career victory.
Several boxing experts felt the challenger, thirty-one, deserved the win but the Derbyshire fighter suffered the second defeat of his 28-fight professional journey.
Buatsi Secures Win in Uneventful Match
The fighter's advancement has plateaued in recent times through management issues and extended periods of inactivity.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under fresh management.
He opened tentatively, with the two boxers willing to take risks in a cagey initial rounds.
Parker, whose sole prior loss came at super-middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at the higher weight class.
By the fight's midpoint, Parker had made it competitive, causing problems for the favorite, who worked behind a tight guard to edge the more effective rounds.
The audience's tolerance decreased during frequent holding, with Parker going down various instances during grappling.
The underdog closed well, but many rounds were challenging to assess. However, ex-champion the boxing analyst - providing analysis for the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
Buatsi advances, but with the likes of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Hatton Homage Inspires All-Manchester Battle
In the co-main event, Arthur overcame Bradley Rea by divided decision in a terrific local rivalry battle to capture the continental title.
The stadium fell silent for a profoundly moving tribute prior to the bout as a bell ceremony tolled in remembrance of the city's native Ricky Hatton, who died aged 46 in last month.
It was the first major televised match card in the urban center since Hatton's death. As the concluding sound ended, the stillness became a chant of "there's only one Ricky Hatton".
The action during the bout equaled the sentiment. The eventual winner was knocked down by a powerful punch directly to the face in the early round, rising shakily to his footing on the referee's count.
But the red-colored attire of the fighter soon advanced again. Across the ring, Rea - in opposing blue - was injured soon, significant bruising appearing under his face as the fighters traded punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, fought fire with fire with stinging uppercuts as the intensity rarely dropped over 12 rounds.
The victor edged the verdict with scoring tallies of 114-114, close margin and 115-112, but each competitor were determined and courageous, everything their hero Hatton stood for.
